Method of controlling a liquefracture handpiece

ABSTRACT

A control system for a Liquefracture handpiece that uses output from a surgical console to generate a control signal for an RF amplifier. The output from the RF amplifier is used to drive the handpiece heating element. To prevent excessive heated fluid from entering the eye, the vacuum in the handpiece is monitored and excessive or rapid increases in vacuum level (indicating an occlusion or low aspiration flow) causes the power to the heating element to be reduces or eliminated.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 09/130,403 now abandoned, filed Aug. 6, 1998, whichis a continuation-in-part application of U.S. patent application Ser.No. 09/090,433, now U.S. Pat. No. 6,080,128 filed Jun. 4, 1998.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of cataract surgery andmore particularly to a control system for a handpiece for practicing theLiquefracture technique of cataract removal.

The human eye in its simplest terms functions to provide vision bytransmitting light through a clear outer portion called the cornea, andfocusing the image by way of the lens onto the retina. The quality ofthe focused image depends on many factors including the size and shapeof the eye, and the transparency of the cornea and lens.

When age or disease causes the lens to become less transparent, visiondeteriorates because of the diminished light which can be transmitted tothe retina. This deficiency in the lens of the eye is medically known asa cataract. An accepted treatment for this condition is surgical removalof the lens and replacement of the lens fiction by an artificialintraocular lens (IOL).

In the United States, the majority of cataractous lenses are removed bya surgical technique called phacoemulsification. During this procedure,a thin phacoemulsification cutting tip is inserted into the diseasedlens and vibrated ultrasonically. The vibrating cutting tip liquifies oremulsifies the lens so that the lens may be aspirated out of the eye.The diseased lens, once removed, is replaced by an artificial lens.

A typical ultrasonic surgical device suitable for ophthalmic proceduresconsists of an ultrasonically driven handpiece, an attached cutting tip,and irrigating sleeve and an electronic control console. The handpieceassembly is attached to the control console by an electric cable andflexible tubings. Through the electric cable, the console varies thepower level transmitted by the handpiece to the attached cutting tip andthe flexible tubings supply irrigation fluid to and draw aspirationfluid from the eye through the handpiece assembly.

The operative part of the handpiece is a centrally located, hollowresonating bar or horn directly attached to a set of piezoelectriccrystals. The crystals supply the required ultrasonic vibration neededto drive both the horn and the attached cutting tip duringphacoemulsification and are controlled by the console. The crystal/hornassembly is suspended within the hollow body or shell of the handpieceby flexible mountings. The handpiece body terminates in a reduceddiameter portion or nosecone at the body's distal end. The nosecone isexternally threaded to accept the irrigation sleeve. Likewise, the hornbore is internally threaded at its distal end to receive the externalthreads of the cutting tip. The irrigation sleeve also has an internallythreaded bore that is screwed onto the external threads of the nosecone.The cutting tip is adjusted so that the tip projects only apredetermined amount past the open end of the irrigating sleeve.Ultrasonic handpieces and cutting tips are more fully described in U.S.Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583;4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and5,359,996, the entire contents of which are incorporated herein byreference.

In use, the ends of the cutting tip and irrigating sleeve are insertedinto a small incision of predetermined width in the cornea, sclera, orother location. The cutting tip is ultrasonically vibrated along itslongitudinal axis within the irrigating sleeve by the crystal-drivenultrasonic horn, thereby emulsifying the selected tissue in situ. Thehollow bore of the cutting tip communicates with the bore in the hornthat in turn communicates with the aspiration line from the handpiece tothe console. A reduced pressure or vacuum source in the console draws oraspirates the emulsified tissue from the eye through the open end of thecutting tip, the cutting tip and horn bores and the aspiration line andinto a collection device. The aspiration of emulsified tissue is aidedby a saline flushing solution or irrigant that is injected into thesurgical site through the small annular gap between the inside surfaceof the irrigating sleeve and the cutting tip.

Recently, a new cataract removal technique has been developed thatinvolves the injection of hot (approximately 45° C. to 105° C.) water orsaline to liquefy or gellate the hard lens nucleus, thereby making itpossible to aspirate the liquefied lens from the eye. Aspiration isconducted with the injection of the heated solution and the injection ofa relatively cool solution, thereby quickly cooling and removing theheated solution. This technique is more fully described in U.S. Pat. No.5,616,120 (Andrew, et al.), the entire contents of which is incorporatedherein by reference. The apparatus disclosed in the publication,however, heats the solution separately from the surgical handpiece.Temperature control of the heated solution can be difficult because thefluid tubings feeding the handpiece typically are up to two meters long,and the heated solution can cool considerably as it travels down thelength of the tubing.

Therefore, a need continues to exist for a control system for a surgicalhandpiece that can heat internally the solution used to perform theLiquefracture technique.

BRIEF SUMMARY OF THE INVENTION

The present invention improves upon the prior art by providing a controlsystem for a Liquefracture handpiece. The system uses output from asurgical console to generate a control signal for an RF amplifier. Theoutput from the RF amplifier is used to drive the handpiece heatingelement. To prevent excessive heated fluid from entering the eye, thevacuum in the aspiration tubing is monitored and excessive or rapidincreases in vacuum level (indicating an occlusion) causes the power tothe heating element to be reduces or eliminated.

Accordingly, one objective of the present invention is to provide asurgical console control system.

Another objective of the present invention is to provide a surgicalconsole control system that generates a control signal for an RFamplifier.

Another objective of the present invention is to provide a surgicalconsole control system that provided a drive signal for a Liquefracturehandpiece.

These and other advantages and objectives of the present invention willbecome apparent from the detailed description and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front, upper left perspective view of the handpiece of thepresent invention.

FIG. 2 is a rear, upper right perspective view of the handpiece of thepresent invention.

FIG. 3 is a cross-sectional view of the handpiece of the presentinvention taken along a plane passing through the irrigation channel.

FIG. 4 is a cross-sectional view of the handpiece of the presentinvention taken along a plane passing through the aspiration channel.

FIG. 5 is an enlarged partial cross-sectional view of the handpiece ofthe present invention taken at circle 5 in FIG. 4.

FIG. 6 is an enlarged partial cross-sectional view of the handpiece ofthe present invention taken at circle 6 in FIG. 3.

FIG. 7 is an enlarged cross-sectional view of the handpiece of thepresent invention taken at circle 7 in FIGS. 3 and 4, and showing aresistive boiler pump.

FIG. 8 is a schematic cross-sectional view of a heating element boilerpump that may be used with the present invention.

FIG. 9 is an exploded, partial cross-section view of one embodiment ofthe handpiece of the present invention.

FIG. 10 is a block diagram of a control system that can be used with thehandpiece of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Handpiece 10 of the present invention generally includes handpiece body12 and operative tip 16. Body 12 generally includes external irrigationtubing 18 and aspiration fitting 20. Body 12 is similar in constructionto well-known in the art phacoemulsification handpieces and may be madefrom plastic, titanium or stainless steel. As best seen in FIG. 6,operative tip 16 includes tip/cap sleeve 26, needle 28 and tubing 30.Sleeve 26 may be any suitable commercially available phacoemulsificationtip/cap sleeve or sleeve 26 may be incorporated into other tubes as amulti-lumen tube. Needle 28 may be any commercially available hollowphacoemulsification cutting tip, such as the TURBOSONICS tip availablefrom Alcon Laboratories, Inc., Fort Worth, Tex. Tubing 30 may be anysuitably sized tubing to fit within needle 28, for example 29 gaugehypodermic needle tubing.

As best seen in FIG. 5, tubing 30 is free on the distal end andconnected to pumping chamber 42 on the proximal end. Tubing 30 andpumping chamber 42 may be sealed fluid tight by any suitable meanshaving a relatively high melting point, such as silver solder. Fitting44 holds tubing 30 within bore 48 of aspiration horn 46. Bore 48communicates with fitting 20, which is journaled into horn 46 and sealedwith O-ring seal 50 to form an aspiration pathway through horn 46 andout fitting 20. Horn 46 is held within body 12 by O-ring seal 56 to formirrigation lumen 52 which communicates with irrigation tubing 18 at port54.

As best seen in FIG. 7, in a first embodiment of the present invention,pumping chamber 42 contains a relatively large pumping reservoir 43 thatis sealed on both ends by electrodes 45 and 47. Electrical power issupplied to electrodes 45 and 47 by insulated wires 49 and 51,respectively. In use, surgical fluid (e.g. saline irrigating solution)enters reservoir 43 through port 55, tubing 34 and check valve 53, checkvalves 53 being well-known in the art. Electrical current (preferablyRadio Frequency Alternating Current or RFAC) is delivered to and acrosselectrodes 45 and 47 because of the conductive nature of the surgicalfluid. As the current flows through the surgical fluid, the surgicalfluid boils. As the surgical fluid boils, it expands rapidly out ofpumping chamber 42 through port 57 and into tubing 30 (check valve 53prevents the expanding fluid from entering tubing 34). The expanding gasbubble pushes the surgical fluid in tubing 30 downstream of pumpingchamber 42 forward. Subsequent pulses of electrical current formsequential gas bubbles that move surgical fluid down tubing 30. The sizeand pressure of the fluid pulse obtained by pumping chamber 42 can bevaried by varying the length, timing and/or power of the electricalpulse sent to electrodes 45 and 47 and by varying the dimensions ofreservoir 43. In addition, the surgical fluid may be preheated prior toentering pumping chamber 42. Preheating the surgical fluid will decreasethe power required by pumping chamber 42 and/or increase the speed atwhich pressure pulses can be generated.

While several embodiments of the handpiece of the present invention aredisclosed, any handpiece producing adequate pressure pulse force, risetime and frequency may also be used. For example, any suitable handpieceproducing a pressure pulse force of between 0.03 grams and 50.0 grams(between 1 gram and 50.0 grams being preferred), with a rise time ofbetween 1 gram/second and 50,000 grams/second (with between 500grams/second and 50,000 grams/second being preferred) and a frequency ofbetween 1 Hz and 200 Hz may be used, with between 10 Hz and 100 Hz beingmost preferred. The pressure pulse force and frequency may be variedwith the hardness of the material being removed. For example, theinventors have found that a lower frequency with a higher pulse force ismore efficient at debulking and removing the relatively hard nuclearmaterial, with a higher frequency and lower pulse force being useful inremoving softer epinuclear and cortical material. Infusion pressure,aspiration flow rate and vacuum limit are similar to currentphacoemulsification techniques.

As best seen in FIG. 8, the fluid in reservoir 143 in pumping chamber142 may also be heated by the use of heating element 145 that isinternal to reservoir 143. Heating element 145 may be, for example, acoil of 0.003 inch diameter stainless steel wire which is energized bypower source 147. The size and pressure of the fluid pulse obtained bypumping chamber 142 can be varied by varying the length and timing ofthe electrical pulse sent to element 145 by control module 147 and byvarying the dimensions of reservoir 143.

As seen in FIG. 10, one embodiment of control system 300 for use inoperating handpiece 310 includes control module 347, power gain RFamplifier 312 and fiction generator 314. Power is supplied to RFamplifier 312 by DC power supply 316, which preferably is an isolated DCpower supply operating at several hundred volts, but typically ±200volts. Control module 347 may be any suitable microprocessor, microcontroller, computer or digital logic controller and may receive inputfrom operator input device 318. Function generator 314 provides theelectric wave form in kilohertz to amplifier 312 and typically operatesat around 450 KHz or above to help minimize corrosion.

In use, control module 347 receives input from surgical console 320.Console 320 may be any commercially available surgical control consolesuch as the LEGACY® SERIES TWENTY THOUSANDS® surgical system availablefrom Alcon Laboratories, Inc., Fort Worth, Tex. Console 320 is connectedto handpiece 310 through irrigation line 322 and aspiration line 324,and the flow through lines 322 and 324 is controlled by the user viafootswitch 326. Irrigation and aspiration flow rate information inhandpiece 310 is provided to control module 347 by console 320 viainterface 328, which may be connected to the ultrasound handpiececontrol port on console 320 or to any other output port. Control module347 uses footswitch 326 information provided by console 320 and operatorinput from input device 318 to generate two control signals 330 and 332.Signal 332 is used to operate pinch valve 334, which controls thesurgical fluid flowing from fluid source 336 to handpiece 310. Fluidfrom fluid source 336 is heated in the manner described herein. Signal330 is used to control function generator 314. Based on signal 330,function generator 314 provides a wave form at the operator selectedfrequency and amplitude determined by the position of footswitch 326 toRF amplifier 312 which is amplified to advance the powered wave formoutput to handpiece 310 to create heated, pressurized pulses of surgicalfluid.

As best seen in FIGS. 3, 4 and 7, surgical fluid may be supplied topumping chamber 43 through tubing 34 or, as seen in FIG. 9, surgicalfluid may be supplied to pumping chamber 243 through irrigation fluidtubing 234 which branches off main irrigation tubing 235 supplying coolsurgical fluid to the operative site. As seen in FIG. 9, aspirationtubing 237 may be contained internally to handpiece 10.

Referring back to FIG. 10, any of a number of methods can be employed inorder limit the amount of heat introduced into the eye. For example, thepulse train duty cycle of the heated solution can be varied so that thetotal amount of heated solution introduced into the eye does not varywith the pulse frequency. Alternatively, the aspiration flow rate can bevaried as a function of pulse frequency so that as pulse frequencyincreases aspiration flow rate increases proportionally. In addition,any unexpected excessive or sharp increase in vacuum level in line 324can indicate an occlusion or low flow in line 324. Reduced aspirationflow in line 324 may allow excessive heat build up within the surgicalsite. To prevent excessive heated fluid from entering the eye in theevent of an occlusion in handpiece 310, aspiration flow rate informationin line 324 is provided to control module 347 by console 320 viainterface 328. Based on a sensed occluded or low flow condition, controlmodule 347 can reduce or cut off the output of amplifier 312, therebyreducing or eliminating the heated fluid entering the surgical site.

This description is given for purposes of illustration and explanation.It will be apparent to those skilled in the relevant art that changesand modifications may be made to the invention described above withoutdeparting from its scope or spirit. For example, it will be recognizedby those skilled in the art that the present invention may be combinedwith ultrasonic and/or rotating cutting tips to enhance performance.

I claim:
 1. A method for controlling a Liquefracture handpiece,comprising the steps of: a) providing a control module capable ofgenerating a control signal; b) providing a function generator thatreceives the control signal, the function generator capable ofgenerating a wave form in response to the control signal; c) providingan amplifier that receives the wave form, the amplifier capable ofamplifying the wave form to provide a power wave form to theLiquefracture handpiece; and d) varying the output of the amplifierbased on aspiration fluid flow levels.
 2. The method of claim 1 whereinthe control module is a microprocessor.
 3. The method of claim 1 whereinthe function generator operates at around 450 KHz or above.
 4. Themethod of claim 1 wherein the amplifier is an RF amplifier.